The present application claims priority to German Patent Application No. 199 50 899.2 filed Oct. 22, 1999 the entirety of which is herein incorporated by reference.
1. Field Of The Invention
The present invention concerns an illuminated optical magnifying device, in particular a magnifying device with an optical focusing unit that can produce a magnified image of an object to be viewed and with an illumination device whose light can at least partially be used to illuminate the object to be lit.
2. The Prior Art
A magnifying device of the type described above is recognized from the German Patent Specification DE 39 15 119 C1. For the magnifying device described therein, which is primarily applicable as a reading lens, the focusing unit consists of a plano-convex lens and a plano-concave lens whose concave surface faces the plane surface of the plano-convex lens so that, except for the outer ring-shaped edge of the plane surface of the plano-convex lens, there is an air gap between the two lenses. The two lenses of this focusing unit describe an essentially circular contour whereby incandescent bulbs are arranged in equal angular intervals along the outer edge of the plano-concave lens. This arrangement is part of the illumination device of the recognized state-of-the-art magnifying device. The light emanating from these incandescent bulbs spreads out through the plano-concave lens and is almost totally reflected off the concave surface bordering the air gap in the direction of the plane surface of the plano-concave lens so that the light emanating from this plane surface can illuminate at a distance from it an object intended to be viewed in magnification by means of a magnifying device constructed as a reading lens. The reading lens described above is provided with a ring-shaped mounting surrounding the focusing unit on which a handle is provided for holding a battery.
A disadvantage for the abovementioned device presents itself in that, due to the relatively high-energy consumption of the incandescent bulbs, the batteries must be changed frequently. Furthermore, one must provide for the possibility of changing the incandescent bulbs since these come with only a limited lifetime. In addition, a considerable drawback is incurred with the device mentioned in directing the light emitted by the incandescent bulbs to the object to be observed by means of reflection from the concave surface of the plano-concave lens. The air gap necessitated by the setup and the arrangement of the plano-concave lens prevent a configuration of the focusing unit that would optimize the optical imaging of the object to be observed.
The basic task of the present invention is the creation of a magnifying device of the type mentioned at the beginning that has a simple configuration and presents small energy expenditure in providing good illumination to an object to be observed.
This is achieved according to the invention by having the illumination device contain at least one luminous diode, which is so arranged in the magnifying device that its light can emerge directly from the magnifying device in the direction of the object to be observed. In contrast to the known state-of-the-art incandescent bulbs, the current consumption of a luminous diode is in general considerably smaller so that a current supply provided in the magnifying device, as for example a battery or rechargeable battery, would only need to be changed quite infrequently. Furthermore, presently available luminous diodes have a lifetime of about 100,000 hours so that the magnifying device can be configured simply since, in contrast to the known state-of-the-art luminous bulbs, changing at least one luminous diode is no longer necessary. In addition, because of the essentially direct light emission in the direction of the object to be observed, a complicated design of the magnifying device is avoided. It is no longer necessary to expend a relatively large amount of effort as with, for example, the above mentioned state of the art in order to direct the light from at least one incandescent bulb as effectively as possible on the object to be observed using, for example, total reflection. The focusing unit can then be configured independently from the function of object illumination as is necessary with the state of the art so that conventional lens errors such as spherical aberration, astigmatism, field curvature, distortion and chromatic aberration can be largely avoided. In addition, by doing away with the illumination function of the focusing unit, its entire geometric lens surface can be used optically.
In a preferred design for carrying out the present invention, at least one luminous diode is designed so that it emits white light, in particular with a color temperature of around 6500 K. It turns out that the quality of an image for the human eye is to a certain extent dependent on the color temperature of the illumination. White light, for example, gives a clearer contrast than yellow light. Thus the use of white luminous diodes, in particular with a color temperature of around 6500 K, would make a particularly good image possible. Light diodes of the type mentioned produce only a small amount of heat during their use, first because of their low energy consumption and second because of their high efficiency in converting electric current into light. The design of the magnifying device can thus dispense with precautions for equalizing thermal stresses. In addition, the region to be observed would be extremely well illuminated by the white neutral light, in particular for an application of the magnifying device according to the invention as a reading lens, with, at the same time, low energy consumption.
In a preferred design for carrying out the present invention, the focusing unit would have an essentially circular cross-section or shape whereby the illumination device would consist of a number of luminous diodes that are arranged around the focusing unit preferably in equal angular intervals. In this way a particularly efficient illumination of the object to be observed is obtained.
The focusing unit can include at least one convex lens and/or at least one achromatic lens that are applicable for the focusing of the object to be observed. As previously mentioned, the focusing unit can be optimized as desired based on its imaging characteristics. For example, the focusing unit can be so arranged that the magnifying device serves as a reading lens.
It is then possible, for example, to provide at least one of the optically functional surfaces of the focusing unit being used for the imaging of the object to be observed with at least one reflection-reducing coating. At least one coating can also be realized as a multiple coating so that the residual reflection in the visible spectral range would be limited to less than 1%, preferably less than 0.5%. In this way, the imaging characteristics can be further improved for the observer.
In a preferred design for carrying out the present invention, the magnifying device can include a handle in which the current supply for at least one luminous diode is located, whereby at least one luminous diode is preferably connected with the current supply by way of a switch located on the handle. A battery or rechargeable battery can be used as current supply. Placing the current supply in a handle gives the magnifying device a compact design.
The focusing unit can be advantageously surrounded with a ring-shaped mounting in which at least one luminous diode is placed. The ring-shaped mounting can then be attached to the abovementioned handle. It is further possible to place openings on the side of the ring-shaped mounting directed toward the object to allow the light from the various luminous diodes to exit. For this, the luminous diodes can be placed, for example, at equal angular intervals around the focusing unit. In this way, the result is a very uncomplicated design for the magnifying device according to the invention since, after all, only a ring-shaped mounting with a handle is provided wherein the luminous diodes used for illumination are placed in simple boreholes in the ring-shaped mounting. In contrast to the quite complicated state of the art, the magnifying device according to the invention produces in this way a more robust, more compact design.
In a preferred design for carrying out the present invention, the focal length of the focusing unit and the beam angle of at least one light diode is matched to each other in such a way that, at an optimal separation of the object to be observed from the focusing unit as given by the focal length of the focusing unit, the object is optimally illuminated by at least one of the luminous diodes. In particular, for several luminous diodes, this would be precisely the case if the light from neighboring luminous diodes already overlaps at the abovementioned optimal separation. This would then avoid having a dark spot appear in the center of the focusing unit because the light of the luminous diodes arranged, for example, in a circle around the focusing unit to not yet overlap in the center of the region to be observed in the object.
In a preferred design for carrying out the present invention, the magnifying device is surrounded by a housing that has, on its side that will be directed toward the object to be observed, a positioning surface for placement on the object to be observed. Such a design for carrying out a magnifying device according to the present invention is particularly appropriate as a dermatoscope since the positioning surface can here be directly placed on the area of the patient""s skin to be examined.
It may be expedient if the focusing unit or part of the focusing unit can be moved toward or away from the direction of the positioning surface. Through this displacement of the focusing unit, the doctor observing the region of the skin or other user of the magnifying device can put the resultant magnified image of the region of the skin in sharp focus.
As an alternative to the abovementioned embodiments, a magnifying device according to the invention can also be implemented as a large-surface viewing device, and in particular as a watchmaker""s lens or something similar.